Herein, we introduce a new thermal contrast enhancement procedure for infrared images, acquired from a non-destructive evaluation of composite slabs through active infrared thermography experiments. This technique can compensate for the vignetting effect, as well as the non-uniform heating produced by the thermal excitation scheme. The proposed technique does not depend on any heat propagation model but almost exclusively on experimental data, because it is based on an unsharp mask operation using a median filter. The preliminary results show that real and apparent non-uniform heating is effectively compensated with this method, resulting in better images of possible internal defects than other classic methods like Differential Absolute Contrast DAC, and therefore increasing the probability of more efficient detection and characterization procedures; specifically, the non-uniformity effect on the original sequence could be reduced by about 74%, according to a non-uniformity parameter defined in this work, as well.

Introducción

NON-UNIFORM HEATING COMPENSATION FOR SEQUENCES OF
THERMAL IMAGES USING MEDIAN FILTERING
COMPENSACIÓN DEL CALENTAMIENTO NO UNIFORME EN
SECUENCIAS DE IMÁGENES TÉRMICAS MEDIANTE FILTRADO
DE MEDIANA
ANDRÉS DAVID RESTREPO GIRÓN
M.Sc., Universidad Santiago de Cali, Campus Pampalinda, Cali, Valle, Colombia, adareg378@gmail.com
HUMBERTO LOAIZA CORREA
Ph.D.,Universidad del Valle, Ciudad Universitaria Meléndez, Cali, Valle, Colombia, humberto.loaiza@correounivalle.edu.co
Received for review February 5th, 2012, accepted December 14th, 2012, final version January, 21 th, 2013
ABSTRACT: Herein, we introduce a new thermal contrast enhancement procedure for infrared images, acquired from a non-destructive
evaluation of composite slabs through active infrared thermography experiments. This technique can compensate for the vignetting effect,
as well as the non-uniform heating produced by the thermal excitation scheme. The proposed technique does not depend on any heat
propagation model but almost exclusively on experimental data, because it is based on an unsharp mask operation using a median filter. The
preliminary results show that real and apparent non-uniform heating is effectively compensated with this method, resulting in better images
of possible internal defects than other classic methods like Differential Absolute Contrast (DAC), and therefore increasing the probability of
more efficient detection and characterization procedures; specifically, the non-uniformity effect on the original sequence could be reduced
by about 74%, according to a non-uniformity parameter defined in this work, as well.
KEYWORDS: infrared thermography, active infrared thermography, thermal contrast, non-uniform heating, vignetting, unsharp masking,
median filter.
RESUMEN: Se expone un nuevo procesamiento para el mejoramiento del contraste térmico en una secuencia de imágenes infrarrojas
adquiridas a partir de un procedimiento de Termografía IR activa sobre placas de material compuesto, capa...